Refrigerating machine oil composition

ABSTRACT

The invention provides a refrigerating machine oil composition by which a capillary tube is hardly clogged when a hydrofluorocarbon type, a hydrocarbon type, an ether type, a carbon dioxide type or an ammonia type is used as a refrigerant. It is a refrigerating machine oil composition in which base oil containing at least one oxygen-containing synthetic oil selected from a polyvinyl ether and a polyol ester is mixed with 1 to 20% by weight, based on the total amount of the composition, of a specific polyalkylene glycol alkyl ether or 1 to 40% by weight, based on the total amount of the composition, of an alkylbenzene having a number average molecular weight of 100 to 1,000.

This application is a 371 of PCT/SP99/02449 filed May 12, 1999.

TECHNICAL FIELD

The present invention relates to a refrigerating machine oilcomposition. More specifically, it relates to a refrigerating machineoil composition having good properties that a capillary tube is hardlyclogged and so forth when a hydrofluorocarbon type, a fluorocarbon type,a hydrocarbon type, an ether type, a carbon dioxide type or an ammoniatype, preferably a hydrofluorocarbon type which can be a substitute fora chlorofluocarbon type refrigerant problematic due to the environmentalpollution is used as a refrigerant.

BACKGROUND OF THE INVENTION

Generally, a compression-type refrigerating machine comprises at least acompressor, a condenser, an expansion mechanism (expansion valve and thelike), an evaporator and further a drier, having a structure that amixed liquid of a refrigerant and lubricating oil is circulated in thisclosed system. As a refrigerant of a compression-type refrigeratingmachine, especially, an air-conditioner, chlorodifluoromethane(hereinafter referred to as R22) or a mixture of chlorodifluoromethaneand chloropentafluoroethane at a weight ratio of 48.8:51.2 (hereinafterreferred to as R502) has been of ten used so far. Further, aslubricating oil, various mineral oils or synthetic oils that meet theabove-described requirements have been used. However, since there is afear that R22 and R502 might cause the environmental pollution such asthe depletion of the ozonosphere present in the stratosphere or thelike, they are being strictly regulated worldwide. For this reason,hydrofluorocarbons typified by 1,1,1,2-tetrafluoroethane,difluoromethane, pentafluoroethane and 1,1,1-trifluoroethane(hereinafter referred to as R134a, R32, R125 and R143a respectively)have attracted much interest as new refrigerants, and are replacing thesame. Since there is no fear that these hydrofluorocarbons, especiallyR134a, R32, R125 and R143a might deplete the ozonosphere, they arepreferable as a refrigerant for a compression-type refrigeratingmachine. Nevertheless, it is problematic when the hydrofluorocarbons areused singly. For example, in “Energy-Resources”, vol. 16, No. 5, p. 474,it is reported that (1) when R134a is applied to an air-conditioner as asubstitute for R22, an operating pressure is low, and an ability isdecreased by approximately 40% and an efficiency by approximately 5% ascompared with R22, (2) in comparison with R22, R32 is good inefficiency, but an operating pressure is high and a slightcombustibility is shown , (3) R125 is incombustible, but a criticalpressure is low and an efficiency is decreased, and so forth. Further,R143a is, like R32, problematic in a combustibility.

It is preferable that the refrigerant for the compression-typerefrigerating machine can be used without changing the existingrefrigerating machine. However, in view of the foregoing problems, arefrigerant containing the above-described hydrofluorocarbon has to beactually used. That is, in order to substitute existing refrigerants R22and R502, it is advisable that combustible R32 and R143a are used fromthe aspect of the efficiency and the former is mixed with R125 and R134afor imparting an incombustibility to the entire refrigerant. In TheInternational Symposium on R22 & R502 Alternative Refrigerants, 1994, p.166, it is indicated that an R32/R134a mixture is combustible with theR32 content of 56% by weight or more. It is said that a refrigerantcontaining 45% by weight or more of an incombustible hydrofluorocarbonsuch as R125, R134a or the like is preferable from the aspect of theincombustibility, which cannot absolutely be defined though in view ofthe refrigerant composition.

Meanwhile, since a refrigerant is used under various conditions within arefrigerating system, it is undesirable that compositions ofhydrofluorocarbons to be mixed vary greatly in respective positions ofthe refrigerating system. A refrigerant takes both gaseous and liquidforms in the refrigerating system. Accordingly, when boiling points ofhydrofluorocarbons to be mixed are quite different, there is apossibility that compositions of mixing refrigerants vary greatly inrespective positions of the refrigerating system for the foregoingreason.

The boiling points of R32, R143a, R125 and R134a are −51.7° C., −47.4°C., −48.5° C. and −26.3° C. respectively. When R134a is used in ahydrofluorocarbon-containing refrigerant system, care must be taken inthis respect. Accordingly, in a refrigerant containing R125, its contentis between 20 and 80% by weight, especially preferably between 40 and70% by weight. When the content is less than 20% by weight, a largeamount of a refrigerant having quite a different boiling point, such asR134a or the like, is further required to impart an incombustibility,which is undesirable in view of the foregoing reason. Further, when thecontent of R125 exceeds 80% by weight, an efficiency is decreased. Thus,it is unwanted.

In view of these points, as a substitute for the existing R22refrigerant, a mixture of R32, R125 and R134a at a weight ratio of23:25:52 (hereinafter referred to as R407C), a mixture thereof at aweight ratio of 25:15:60, a mixture of R32 and R125 at a weight ratio of50:50 (hereinafter referred to as R410A), and a mixture of R32 and R125at a weight ratio of 45:55 (hereinafter referred to as R410B) arepreferable. Meanwhile, as a substitute for the R502 refrigerant, amixture of R125, R143a and R134a at a weight ratio of 44:52:4(hereinafter referred to as R404A) and a mixture of R125 and R143a at aweight ratio of 50:50 (hereinafter referred to as R507) are preferable.

This hydrofluorocarbon refrigerant is different from ordinaryrefrigerants in qualities. As refrigerating machine oil used incombination with this, a product obtained by using, for example, apolyalkylene glycol, a polyol ester, a polyvinyl ether or the likehaving a specific structure as base oil and adding thereto additivessuch as an antioxidant, an extreme pressure agent, a defoamer and thelike is known to be useful.

On the other hand, in a refrigerating machine, an expansion valve calleda capillary tube is provided in a refrigerating cycle. Since thiscapillary tube is a narrow tube having a diameter of approximately 0.7mm, it tends to clog. The clogging phenomenon of the capillary tube isthe most serious factor to determine the life of the refrigeratingcycle. However, owing to the use of the additives, sludges wereaccumulated, and these caused the clogging of the capillary tube.Accordingly, the development of additives for dissolving materials thatclog the capillary has been expected, and the advent of a refrigeratingoil composition containing the same has been in demand.

DISCLOSURE OF THE INVENTION

The invention has been made from these aspects, and it aims to provide arefrigerating machine oil composition by which a capillary tube ishardly clogged when a hydrofluorocarbon type, a hydrocarbon type, anether type, a carbon dioxide type or an ammonia type, preferably ahydrofluorocarbon type which can be a substitute for a chlorofluocarbontype refrigerant problematic due to the environmental pollution is usedas a refrigerant.

The present inventors have assiduously conducted investigations, andhave consequently found that the aim of the invention can effectively beachieved by mixing base oil containing oxygen-containing synthetic oilsuch as a polyvinyl ether or a polyol ester with a specific polyalkyleneglycol alkyl ether or alkylbenzene. This has led to the completion ofthe invention.

That is, the gist of the invention is as follows.

First Invention

(1) A refrigerating machine oil composition characterized in that a baseoil containing at least one oxygen-containing synthetic oil selectedfrom the group consisting a polyvinyl ether and a polyol ester is mixedwith 1 to 20% by weight, based on the total amount of the composition,of a polyalkylene glycol alkyl ether having a number average molecularweight of 500 to 3,000, as represented by the following general formula(I) or (II)

R¹—O—(EO)_(m)(PO)_(n)—R²  (I)

R¹—O—(EO)_(m)(BO)_(n)—R²  (II)

(wherein EO represents an oxyethylene group, PO represents anoxypropylene group, BO represents an oxybutylene group, m and n eachrepresent a positive number that satisfies the molecular weight, and R¹and R² each represent hydrogen or an alkyl group with 1 to 10 carbonatoms, provided R¹ and R² may be the same but are not hydrogens at thesame time).

(2) A refrigerating machine oil composition characterized in that baseoil containing a polyvinyl ether copolymer comprising a structural unit(A) represented by the following general formula (XVII)

(wherein R⁴³ represents a hydrocarbon group with 1 to 3 carbon atomshaving or not having an ether linkage in a molecule)

and/or a structural unit (B) represented by the following generalformula (XVIII)

(wherein R⁴⁴ represents a hydrocarbon group with 3 to 20 carbon atomshaving or not having an ether linkage in a molecule)

[provided R⁴³ of the structural unit (A) and R⁴⁴ of the structural unit(B) are not the same]

is mixed with 1 to 20% by weight, based on the total amount of thecomposition, of a polyalkylene glycol alkyl ether having a numberaverage molecular weight of 500 to 3,000, as represented by thefollowing general formula (I) or (II)

R¹—O—(EO)_(m)(PO)_(n)—R ²  (I)

R¹—O—(EO)_(m)(BO)_(n)—R ²  (II)

(wherein EO represents an oxyethylene group, PO represents anoxypropylene group, BO represents an oxybutylene group, m and n eachrepresent a positive number that satisfies the molecular weight, and R¹and R² each represent hydrogen or an alkyl group with 1 to 10 carbonatoms, provided R¹ and R² may be the same but are not hydrogens at thesame time).

Second Invention

(3) A refrigerating machine oil composition characterized in that a baseoil containing at least one oxygen-containing synthetic oil selectedfrom the group consisting of a polyvinyl ether and a polyol ester ismixed with 1 to 40% by weight, based on the total amount of thecomposition, of an alkylbenzene having a number average molecular weightof 100 to 1,000.

(4) A refrigerating machine oil composition characterized in that baseoil containing a polyvinyl ether copolymer comprising a structural unit(A) represented by the following general formula (XVII)

(wherein R⁴³ represents a hydrocarbon group with 1 to 3 carbon atomshaving or not having an ether linkage in a molecule)

and/or a structural unit (B) represented by the following generalformula (XVIII)

(wherein R⁴⁴ represents a hydrocarbon group with 3 to 20 carbon atomshaving or not having an ether linkage in a molecule)

[provided R⁴³ of the structural unit (A) and R⁴⁴ of the structural unit(B) are not the same]

is mixed with 1 to 40% by weight, based on the total amount of thecomposition, of an alkylbenzene having a number average molecular weightof 100 to 1,000.

BEST MODE FOR CARRYING OUT THE INVENTION

The mode for carrying out the invention is described below.

First, in the refrigerating machine oil composition of the invention,oxygen-containing synthetic oil selected from a polyvinyl ether and apolyol ester is used as base oil. The viscosity of this synthetic oil isnot particularly limited. The kinematic viscosity at 40° C. is between 2and 500 mm²/s, preferably between 5 and 200 mm²/s, more preferablybetween 10 and 100 mm²/s. Further, the pour point, an index of alow-temperature fluidity of this base oil is not particularly limited.It is preferably −10° C. or less. The oxygen-containing synthetic oilwill be described last in detail.

Next, a polyalkylene glycol alkyl ether and an alkylbenzene to be mixedwith the base oil is described.

The polyalkylene glycol alkyl ether which is an additive of the firstinvention of the application has a number average molecular weight of500 to 3,000, and is represented by the general formula (I) or (II).

In the general formula (I) or (II), R¹ and R² are each hydrogen or analkyl group with 1 to 10 carbon atoms. This alkyl group may be linear orbranched. Specific examples of the alkyl group can include methyl,ethyl, n-propyl, isopropyl, various butyl, various pentyl, varioushexyl, various heptyl, various octyl, various nonyl and various decylgroups. When the number of carbon atoms of this alkyl group exceeds 10,the solubility in base oil is poor. Thus, it is undesirable. Thepreferable number of carbon atoms of the alkyl group is between 1 and 6.The more preferable number of carbon atoms of the alkyl group is 3 or 4.Incidentally, R¹ and R² may be the same, but are not hydrogens at thesame time. Further, a polyalkylene glycol monoalkyl ether in which oneof R¹ and R² is hydrogen is especially preferable. In this case, R¹ orR² is preferably a propyl group or a butyl group.

In the general formula (I) or (II), EO and PO or EO and BO may be in arandom form or in a block form. Further, m and n are each a positivenumber that satisfies the molecular weight, and an m/n ratio ispreferably in the range of 5/95 to 40/60.

In the invention, the number average molecular weight of thepolyalkylene glycol alkyl ether represented by the general formula (I)or (II) has to be between 500 and 3,000. When it is less than 500, thevolume resistivity is decreased, and the electrical insulationproperties are worsened. Further, when it exceeds 3,000, thecompatibility with the refrigerant is decreased. Thus, it isundesirable. It is preferably between 800 and 2,000. Still further, themolecular weight distribution is preferably 200 to 10,000. Furthermore,the kinematic viscosity at 40° C. is preferably between 10 and 200mm²/s, more preferably between 30 and 100 mm²/s.

In the refrigerating oil composition of the first invention of theapplication, the polyalkylene glycol alkyl ethers may be used eithersingly or in combination. Further, the mixing amount thereof is between1 and 20% by weight based on the total amount of the composition. Whenthis mixing amount is less than 1% by weight, the aim of the inventionis not achieved satisfactorily. When it exceeds 20% by weight, thevolume resistivity is decreased, and the electrical insulationproperties are worsened. The preferable mixing amount is in the range of2 to 15% by weight.

The alkylbenzene, the additive of the second invention of theapplication is then described.

With respect to the alkylbenzene, the structure is not particularlylimited so long as the number average molecular weight is between 100and 1,000. When the number average molecular weight is less than 100,the effect of preventing the clogging of the capillary is low. When itexceeds 1,000, the compatibility with the refrigerant is decreased.Thus, it is undesirable. Further, the molecular weight distribution ispreferably between 500 and 3,000. Still further, the kinematic viscosityat 40° C. is preferably between 2 and 100 mm²/s, more preferably between5 and 70 mm²/s.

With respect to the structure of the alkylbenzene, a compound having 1to 4 alkyl groups with 4 to 20 carbon atoms is preferable. Specificexamples of the alkyl group can include methyl, ethyl, n-propyl,isopropyl, various butyl, various pentyl, various hexyl, various heptyl,various octyl, various nonyl, various decyl, various undecyl, variousdodecyl, various tridecyl, various tetradecyl, various pentadecyl,various hexadecyl, various heptadecyl, various octadecyl, variousnonadecyl and eicosyl groups. The alkyl group may be linear or branched.In view of the stability, the viscosity characteristics and the like,the branched alkyl group is preferable. Especially in view of theavailability, a branched alkyl group derived from an oligomer such aspropylene, butene, isobutylene or the like is more preferable. Thenumber of the alkyl groups of the alkylbenzene is preferably 1 to 4, andan alkylbenzene having 1 or 2 alkyl groups, namely, a monoalkylbenzene,a dialkylbenzene or a mixture thereof is used most preferably in view ofthe stability and the availability.

In the refrigerating machine oil composition of the second invention ofthe application, the alkylbenzenes may be used either singly or incombination. Further, the mixing amount thereof is between 1 and 40% byweight based on the total amount of the composition. When the mixingamount is less than 1% by weight, the aim of the invention is notachieved satisfactorily. When it exceeds 40% by weight, the effect isnot so improved in spite of this large amount, and the compatibilitywith the refrigerant is decreased. The preferable mixing amount is inthe range of 5 to 35% by weight.

The refrigerating machine oil composition of the invention can contain,as required, various known additives, for example, extreme pressureagents such as a phosphate ester, a phosphite ester and the like;phenolic and amine antioxidants; further acid trapping agents such asphenyl glycidyl ether, cyclohexene oxide, an epoxy compound, forexample, epoxidized soybean oil and the like; copper inactivating agentssuch as benzotriazole, benzotriazole derivatives and the like; anddefoamers such as silicone oil, fluorinated silicone oil and the like.The mixing amount of each of the additives is between 0.01 and 2% byweight based on the total amount of the refrigerating machine oilcomposition.

As the refrigerant used in the refrigerating machine to which therefrigerating machine oil composition of the invention is applied, ahydrofluorocarbon-type, fluorocarbon-type, hydrocarbon-type, ether-type,carbon dioxide-type or ammonia-type refrigerant is used. Of these, ahydrofluorocarbon-type refrigerant is preferable. As thishydrofluorocarbon-type refrigerant, for example, 1,1,2-tetrafluoroethane(R134a), difluoromethane (R32), pentafluoroethane (R125) and1,1,1-trifluoroethane (R143a) are preferable. They may be used eithersingly or in combination. There is no fear that these hydrofluorocarbonsmight deplete the ozonosphere, and they are preferable as therefrigerant for the compression refrigerating machine. Further, examplesof the mixed refrigerant include a mixture of R32, R125 and R134a at aweight ratio of 23:25:52 (hereinafter referred to as R407C), a mixturethereof at a weight ratio of 25:15:60, a mixture of R32 and R125 at aweight ratio of 50:50 (hereinafter referred to as R410A), a mixture ofR32 and R125 at a weight ratio of 45:55 (hereinafter referred to asR410B), a mixture of R125, R143a and R134a at a weight ratio of 44:52:4(hereinafter referred to as R404A), a mixture of R125 and R143a at aweight ratio of 50:50 (hereinafter referred to as R507) and the like.

Finally, the oxygen-containing synthetic oil used as the base oil of therefrigerating machine oil composition of the invention is described indetail.

The polyvinyl ether includes, for example, a polyvinyl ether compound(1) represented by the general formula (III)

(wherein R³ to R⁵ each represent a hydrogen atom or a hydrocarbon groupwith 1 to 8 carbon atoms, they may be same or different, R⁶ represents adivalent hydrocarbon group with 1 to 10 carbon atoms or anether-linkage-oxygen-containing divalent hydrocarbon group with 2 to 20carbon atoms, R⁷ represents a hydrocarbon group with 1 to 20 carbonatoms, a represents is a number with the average value of 0 to 10, R³ toR⁷ may be the same or different in each structural unit, and when thereare plural R⁶O's, plural R⁶O's may be the same or different).

Further, a polyvinyl ether compound (2) made of a block or randomcopolymer having the structural unit represented by the general formula(III) and a structural unit represented by the following general formula(IV)

(wherein R⁸ to R¹¹ each represent a hydrogen atom or a hydrocarbon groupwith 1 to 20 carbon atoms, they may be the same or different, and R⁸ toR¹¹ may be the same or different in each structural unit)

can be used. Still further, a polyvinyl ether compound (3) made of amixture of the polyvinyl ether compound (1) and the polyvinyl ethercompound (2) can also be used. R³ to R⁵ in the general formula (III)each represent a hydrogen atom or a hydrocarbon group with 1 to 8 carbonatoms, preferably with 1 to 4 carbon atoms. Examples of the hydrocarbongroup here referred to can include alkyl groups such as methyl, ethyl,n-propyl, isopropyl, various butyl, various pentyl, various hexyl,various heptyl and various octyl groups, cycloalkyl groups such ascyclopentyl, cyclohexyl, various methylcyclohexyl, variousethylcyclohexyl and various dimethylcyclohexyl groups, aryl groups suchas phenyl, various methylphenyl, various ethylphenyl and variousdimethylphenyl groups, and arylalkyl groups such as benzyl, variousphenylethyl and various methylbenzyl groups. By the way, as these R³ toR⁵, a hydrogen atom is especially preferable.

On the other hand, R⁶ in the general formula (II) represents a divalenthydrocarbon group with 1 to 10 carbon atoms, preferably with 2 to 10carbon atoms or an ether-linkage-oxygen-containing divalent hydrocarbongroup with 2 to 20 carbon atoms. Specific examples of the divalenthydrocarbon group with 1 to 10 carbon atoms here can include divalentaliphatic groups such as methylene, ethylene, phenylethylene,1,2-propylene, 2-phenyl-1,2-propylene, 1,3-propylene, various butylene,various pentylene, various hexylene, various heptylene, variousoctylene, various nonylene and various decylene groups; alicyclic groupsin which 2 bonding sites are present in alicyclic hydrocarbons such ascyclohexane, methylcyclohexane, ethylcyclohexane, dimethylcyclohexane,propylcyclohexane and the like; divalent aromatic hydrocarbon groupssuch as various phenylene, various methylphenylene, variousethylphenylene, various dimethylphenylene and various naphthylene groupsand the like; alkyl aromatic groups in which monovalent bonding sitesare present respectively in an alkyl moiety and an aromatic moiety ofalkyl aromatic hydrocarbons such as toluene, xylene, ethylbenzene andthe like; alkyl aromatic groups in which a bonding site is present in analkyl group moiety of polyalkyl aromatic hydrocarbons such as xylene,diethylbenzene and the like; and so forth. Of these, aliphatic groupswith 2 to 4 carbon atoms are especially preferable.

Moreover, specific preferable examples of theether-linkage-oxygen-containing divalent hydrocarbon group with 2 to 20carbon atoms can include a methoxymethylene group; a methoxyethylenegroup; a methoxymethylene group; a 1,1-bismethoxymethylethylene group; a1,2-bismethoxymethylethylene group; an ethoxymethylethylene group; a(2-methoxyethoxy)methylethylene group; a (1-methyl-2-methoxy)methylenegroup; and the like. By the way, a in the general formula (II)represents the number of R⁶O recurring units, and the average valuethereof is between 0 and 10, preferably between 0 and 5. When there areplural R⁶O's, plural R⁶O's may be the same or different.

In addition, R⁷ in the general formula (III) represents a hydrocarbongroup with 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms.Specific examples of the hydrocarbon group include alkyl groups such asmethyl, ethyl, n-propyl, isopropyl, various butyl, various pentyl,various hexyl, various heptyl, various octyl, various nonyl and variousdecyl groups, cycloalkyl groups such as cyclopentyl, cyclohexyl, variousmethylcyclohexyl, various ethylcyclohexyl, various propylcyclohexyl andvarious dimethylcyclohexyl groups, aryl groups such as phenyl, variousmethylphenyl, various ethylphenyl, various dimethylphenyl, variouspropylphenyl, various trimethylphenyl, various butylphenyl and variousnaphthyl groups, arylalkyl groups such as benzyl, various phenylethyl,various methylbenzyl, various phenylpropyl and various phenylbutylgroups, and the like.

This polyvinyl ether compound (1) has the structural unit represented bythe general formula (III). The number of the recurring units (degree ofpolymerization) can be selected, as required, depending on the desiredviscosity. Further, with respect to the polyvinyl ether compound, acompound having the carbon/oxygen molar ratio of 4.2 to 7.0 ispreferable. When the molar ratio is less than 4.2, the moistureabsorption is sometimes increased. When it exceeds 7.0, thecompatibility with the refrigerant is sometimes decreased.

Moreover, the polyvinyl ether compound (2) is made of the block orrandom copolymer comprising the structural unit represented by thegeneral formula (III) and the structural unit represented by the generalformula (IV). In the general formula (IV), R⁸ to R¹¹ each represent ahydrogen atom or a hydrocarbon group with 1 to 20 carbon atoms, and theymay be the same or different. Examples of the hydrocarbon group with 1to 20 carbon atoms here can include the same as shown in the descriptionof R⁷ in the general formula (III). By the way, R⁸ to R¹¹ may be thesame or different in each structural unit.

The degree of polymerization of the polyvinyl ether compound (2) made ofthe block or random copolymer comprising the structural unit representedby the general formula (III) and the structural unit represented by thegeneral formula (IV) can be selected, as required, according to thedesired viscosity. Further, the carbon/oxygen molar ratio of thispolyvinyl ether compound is preferably in the range of 4.2 to 7.0. Whenthis molar ratio is less than 4.2, the moisture absorption is sometimesincreased. When it exceeds 7.0, the compatibility with the refrigerantis sometimes decreased.

Besides, the polyvinyl ether compound (3) is made of the mixture of thepolyvinyl ether compound (1) and the polyvinyl ether compound (2). Themixing amounts thereof are not particularly limited.

The polyvinyl ether compounds (1) and (2) used in the invention can beproduced by the polymerization of each corresponding vinyl ethermonomer, and the copolymerization of the corresponding hydrocarbonmonomer having the olefinic double bond and the corresponding vinylether monomer. The vinyl ether monomer which can be used here isrepresented by the following general formula (V)

(wherein R³ to R⁷ and a are as defined above). This vinyl ether monomerincludes various monomers corresponding to the polyvinyl ether compounds(1) and (2). Examples thereof include vinylmethyl ether; vinylethylether; vinyl-n-propyl ether; vinylisopropyl ether: vinyl-n-butyl ether;vinylisobutyl ether; vinyl-sec-butyl ether; vinyl-tert-butyl ether;vinyl-n-pentyl ether; vinyl-n-hexyl ether; vinyl-2-methoxyethyl ether;vinyl-2-ethoxyethyl ether; vinyl-2-methoxy-1-methylethyl ether;vinyl-2-methoxy-2-methyl ether; vinyl-3,6-dioxaheptyl ether;vinyl-3,6,9-trioxadecyl ether; vinyl-1,4-dimethyl-3,6-dioxaheptyl ether;vinyl-1,4,7-trimethyl-3,6,9-trioxadecyl ether; vinyl-2,6-dioxa-4-heptylether; vinyl-2,6,9-trioxa-4-decylether; 1-methoxypropene;1-ethoxypropene; 1-n-propoxypropene; 1-isopropoxypropene;1-n-butoxypropene; 1-isobutoxypropene; 1-sec-butoxypropene;1-tert-butoxypropene; 2-methoxypropene; 2-ethoxypropene;2-n-propoxypropene; 2-isopropoxypropene; 2-n-butoxypropene;2-isobutoxypropene; 2-sec-butoxypropene; 2-tert-butoxypropene;1-methoxy-1-butene; 1-ethoxy-1-butene; 1-n-propoxy-1-butene;1-isopropoxy-1-butene; 1-n-butoxy-1-butene; 1-isobutoxy-1-butene;1-sec-butoxy-1-butene; 1-tert-butoxy-1-butene; 2-methoxy-1-butene;2-ethoxy-1-butene; 2-n-propoxy-1-butene; 2-isopropoxy-1-butene;2-n-butoxy-1-butene; 2-isobutoxy-1-butene; 2-sec-butoxy-1-butene;2-tert-butoxy-1-butene; 2-methoxy-2-butene; 2-ethoxy-2-butene;2-n-propoxy-2-butene; 2-isopropoxy-2-butene; 2-n-butoxy-2-butene;2-isobutoxy-2-butene; 2-sec-butoxy-2-butene; 2-tert-butoxy-2-butene; andthe like.

These vinyl ether monomers can be produced by a known method.

Further, a hydrocarbon monomer having an olefinic double bond isrepresented by the following general formula (VI)

(wherein R⁸ to R¹¹ are as defined above).

Examples of this monomer can include ethylene, propylene variousbutenes, various pentenes, various hexenes, various heptenes, variousoctenes, diisobutylene, triisobutylene, styrene, variousalkyl-substituted styrenes and the like.

Preferable examples of the polyvinyl ether compound used in theinvention include compounds having the following end structures, namelya structure that one end thereof is represented by the general formula(VII) or (VIII)

(wherein R¹² to R¹⁴ each represent a hydrogen atom or a hydrocarbongroup with 1 to 8 carbon atoms, R¹² to R¹⁴ may be the same or different,R¹⁷ to R²⁰ each represent a hydrogen atom or a hydrocarbon group with 1to 20 carbon atoms, R¹⁷ to R²⁰ may be the same or different, R¹⁵represents a divalent hydrocarbon group with 1 to 10 carbon atoms or anether-linkage-oxygen-containing divalent hydrocarbon group with 2 to 20carbon atoms, R¹⁶ represents a hydrocarbon group with 1 to 20 carbonatoms, b represents a number with the average value of 0 to 10, and whenthere are plural R¹⁵O's, plural R¹⁵O's may be the same or different)

and the remaining end is represented by the general formula (IX) or (X)

(wherein R²¹ to R²³ each represent a hydrogen atom or a hydrocarbongroup with 1 to 8 carbon atoms, R²¹ to R²³ may be the same or different,R²⁶ to R²⁹ each represent a hydrogen atom or a hydrocarbon group with 1to 20 carbon atoms, R²⁶ to R²⁹ may be the same or different, R²⁴represents a divalent hydrocarbon group with 1 to 10 carbon atoms or anether-linkage-oxygen-containing divalent hydrocarbon group with 2 to 20carbon atoms, R²⁵ represents a hydrocarbon group with 1 to 20 carbonatoms, c represents a number with the average value of 0 to 10, and whenthere are plural R²⁴O's, plural R²⁴O's may be the same or different),

and one end thereof is represented by the general formula (VII) or(VIII) and the remaining end is represented by the general formula (XI)

(wherein R³⁰ to R³² each represent a hydrogen atom or a hydrocarbongroup with 1 to 8 carbon atoms, and they may be the same or different).

Among these polyvinyl ether compounds, the following compounds areespecially preferable as base oil of the refrigerating machine oilcomposition of the invention.

(1) A compound having a structure that one end thereof is represented bythe general formula (VII) or (VIII) and the remaining end is representedby the general formula (IX) or (X), in which in the general formula(III), R³ to R⁵ are both hydrogen atoms, a is a number of 0 to 4, R⁶ isa divalent hydrocarbon group with 2 to 4 carbon atoms and R⁷ is ahydrocarbon group with 1 to 20 carbon atoms.

(2) A compound comprising only a structural unit represented by thegeneral formula (III) and having a structure that one end thereof isrepresented by the general formula (VII) and the remaining end isrepresented by the general formula (IX), in which in the general formula(III), R³ to R⁵ are both hydrogen atoms, a is a number of 0 to 4, R⁶ isa divalent hydrocarbon group with 2 to 4 carbon atoms and R⁷ is ahydrocarbon group with 1 to 20 carbon atoms.

(3) A compound having a structure that one end thereof is represented bythe general formula (VII) or (VIII) and the remaining end is representedby the general formula (XI), in which in the general formula (III), R³to R⁵ are both hydrogen atoms, a is a number of 0 to 4, R⁶ is a divalenthydrocarbon group with 2 to 4 carbon atoms and R⁷ is a hydrocarbon groupwith 1 to 20 carbon atoms.

(4) A compound comprising only a structural unit represented by thegeneral formula (III) and having a structure that one end thereof isrepresented by the general formula (VII) and the remaining end isrepresented by the general formula (X), in which in the general formula(III), R³ to R⁵ are both hydrogen atoms, a is a number of 0 to 4, R⁶ isa divalent hydrocarbon group with 2 to 4 carbon atoms and R⁷ is ahydrocarbon group with 1 to 20 carbon atoms.

Further, in the invention, a polyvinyl ether compound comprising astructural unit represented by the general formula (III) and having astructure that one end thereof is represented by the general formula(VII) and the remaining end is represented by the general formula (XII)

(wherein R³³ to R³⁵ each represent a hydrogen atom or a hydrocarbongroup with 1 to 8 carbon atoms, they may be the same or different, R³⁶and R³⁸ each represent a divalent hydrocarbon group with 2 to 10 carbonatoms, they may be the same or different, R³⁷ and R³⁹ each represent ahydrocarbon group with 1 to 10 carbon atoms, they may be the same ordifferent, d and e each represent a number with the average value of 0to 10, they may be the same or different, when there are plural R³⁶O's,plural R³⁶O's may be the same or different, and when there are pluralR³⁸O's, plural R³⁸O's may be the same or different)

is also available.

Moreover, in the invention, a polyvinyl ether compound made of ahomopolymer or a copolymer of an alkylvinyl ether comprising astructural unit represented by the following general formula (XIII) or(XIV)

(wherein R⁴⁰ represents a hydrocarbon group with 1 to 8 carbon atoms),

having a weight average molecular weight of 300 to 3,000 (preferably 300to 2,000) and having a structure that one end is represented by thegeneral formula (XV) or (XVI)

(wherein R⁴¹ represents an alkyl group with 1 to 3 carbon atoms, and Rrepresents a hydrocarbon group with 1 to 8 carbon atoms)

is also available.

In addition, a polyvinyl ether copolymer comprising a structural unit(A) represented by the following general formula (XVII)

(wherein R⁴³ represents a hydrocarbon group with 1 to 3 carbon atomshaving or not having an ether linkage in a molecule)

and a structural unit (B) represented by the following general formula(XVIII)

(wherein R⁴⁴ represents a hydrocarbon group with 3 to 20 carbon atomshaving or not having an ether linkage in a molecule)

[provided R⁴³ of the structural unit (A) and R⁴⁴ of the structural unit(B) are not the same]

is used especially preferably. A compound in which R⁴³ is an alkyl groupwith 1 to 3 carbon atoms and R⁴⁴ is an alkyl group with 3 to 20 carbonatoms is more preferable. A polyvinyl ether copolymer in which R⁴³ is amethyl group or an ethyl group and R⁴⁴ is an alkyl group with 3 to 6carbon atoms is especially preferable. Among others, a polyvinyl ethercopolymer in which R⁴³ is an ethyl group and R⁴⁴ is an isobutyl group ismost preferable. In this case, the ratio of the structural unit (A) tothe structural unit (B) is preferably in the range of 95:5 to 50:50,more preferably in the range of 95:5 to 70:30 in terms of a molar ratio.

The polyvinyl ether compound can be produced by subjecting the monomerto radical polymerization, cationic polymerization, radiationpolymerization or the like. For instance, the vinyl ether monomer ispolymerized by the following method to obtain a polymer having a desiredviscosity.

In the initiation of the polymer, a combination of Brφnsted acids, Lewisacids or organometallic compounds with water, alcohols, phenols, acetalsor adducts of vinyl ethers and carboxylic acids can be used.

Examples of Brφnsted acids include hydrofluoric acid, hydrochloric acid,hydrobromic acid, hydroiodic acid, nitric acid, sulfuric acid,trichloroacetic acid, trifluoroacetic acid and the like. Examples of theLewis acids include boron trifluoride, aluminum trichloride, aluminumtribromide, tin tetrachloride, zinc dichloride, ferric chloride and thelike. Of these Lewis acids, boron trifluoride is especially preferable.Further, examples of the organometallic compounds includediethylaluminum chloride, ethylaluminum chloride, diethylzinc and thelike.

Water, alcohols, phenols, acetals or adducts of vinyl ethers andcarboxylic acids used in combination therewith can optionally beselected.

Examples of the alcohols here include saturated aliphatic alcohols with1 to 20 carbon atoms, such as methanol, ethanol, propanol, isopropanol,butanol, isobutanol, sec-butanol, tert-butanol, various pentanols,various hexanols, various heptanols, various octanols and the like;unsaturated aliphatic alcohols with 3 to 10 carbon atoms, such as allylalcohol and the like; and so forth.

Examples of the carboxylic acids in using the adducts of the vinylethers and the carboxylic acids include acetic acid; propionic acid;n-butyric acid; isobutyric acid; n-valeric acid; isovaleric acid;2-methylbutyric acid; pivalic acid; n-caproic acid; 2,2-dimethylbutyricacid; 2-methylvaleric acid; 3-methylvaleric acid; 4-methylvaleric acid;enanthic acid; 2-methylcaproic acid; capric acid; 2-ethylcaproic acid;2-n-propylvaleric acid; n-nonanoic acid; 3,5,5-trimethylcaproic acid;capric acid; undecanoic acid; and the like.

Further, the vinyl ethers may be the same as, or different from, thosewhich are used in the polymerization. The adducts of the vinyl ethersand the carboxylic acids can be obtained by mixing both of them andreacting the mixture at a temperature of approximately 0 to 100° C.,separated through distillation and used in the reaction. They can alsobe used as such in the reaction without being separated.

When water, alcohols or phenols are used, hydrogen is bound to thepolymerization initiation end of the polymer. When acetals are used,hydrogen or one alkoxy group from acetals used is eliminated. Further,when adducts of vinyl ethers and carboxylic acids are used, analkylcarbonyloxy group derived from a carboxylic acid moiety iseliminated from adducts of vinyl ethers and carboxylic acids.

On the other hand, when water, alcohols, phenols or acetals are used,the termination end is an acetal, an olefin or an aldehyde. Further, incase of adducts of vinyl ethers and carboxylic acids, it is a carboxylicacid ester of a hemiacetal.

The end of the thus-obtained polymer can be converted to a desired groupby a known method. Examples of the desired group include residues suchas saturated hydrocarbons, ethers, alcohols, ketones, nitrites, amidesand the like. Residues such as saturated hydrocarbons, ethers andalcohols are preferable.

The polymerization of the vinyl ether monomer represented by the generalformula (V) can be initiated at between −80 and 150° C., though itdepends on the types of the starting material and the initiator. It canusually be conducted at a temperature in the range of −80 to 50° C.Further, the polymerization reaction is completed in 10 seconds to 10hours from the initiation of the reaction.

With respect to the adjustment of the molecular weight in thepolymerization reaction, a polymer having a low average molecular weightis obtained by increasing the amount of water, alcohols, phenols,acetals or adducts of vinyl ethers and carboxylic acids relative to thevinyl ether monomer represented by the general formula (V) Moreover, apolymer having a low average molecular weight is obtained by increasingthe amount of the Brφnsted acids or the Lewis acids.

This polymerization reaction is usually conducted in the presence of asolvent. The solvent is not particularly limited so long as it dissolvesa necessary amount of a reaction starting material and is inactive tothe reaction. For example, hydrocarbon solvents such as hexane, benzene,toluene and the like, and ether solvents such as ethyl ether,1,2-dimethoxyethane, tetrahydrofuran and the like can preferably beused. By the way, this polymerization reaction can be completed byadding an alkali. After the completion of the reaction, ordinaryseparation and purification methods are conducted as required to obtaina desired polyvinyl ether compound comprising a structural unitrepresented by the general formula (III).

In the polyvinyl ether compound used in the invention, the carbon/oxygenmolar ratio is preferably in the range of 4.2 to 7.0 as described above.The polymer having the molar ratio in the foregoing range can beproduced by adjusting the carbon/oxygen molar ratio of the startingmonomer. That is, when an amount of a monomer having a highcarbon/oxygen molar ratio is large, a polymer having a highcarbon/oxygen molar ratio is obtained. When an amount of a monomerhaving a low carbon/oxygen molar ratio is large, a polymer having a lowcarbon/oxygen molar ratio is obtained.

Further, as described in the polymerization method of the vinyl ethermonomer, it is also possible with a combination of water, alcohols,phenols, acetals or adducts of vinyl ethers and carboxylic acids used asan initiator and monomers. When alcohols, phenols and the like having ahigher carbon/oxygen molar ratio than the monomer for polymerization areused as an initiator, a polymer having a higher carbon/oxygen molarratio than the starting monomer is obtained. Meanwhile, when alcoholshaving a lower carbon/oxygen molar ratio, such as methanol,methoxyethanol and the like are used, a polymer having a lowercarbon/oxygen molar ratio than the starting monomer is obtained.

Furthermore, when the vinyl ether monomer and the hydrocarbon monomerhaving the olefinic double bond are copolymerized, a polymer having ahigher carbon/oxygen molar ratio than the carbon/oxygen molar ratio ofthe vinyl ether monomer is obtained. The ratio thereof can be adjustedby the ratio of the hydrocarbon monomer having the olefinic double bondor the number of carbon atoms.

The polyol ester includes a carboxylic acid ester of a polyhydrichydroxy compound containing at least two hydroxyl groups. For example, acompound represented by the general formula (XIX)

R⁴⁵[OCOR⁴⁶]_(f)  (XIX)

(wherein R⁴⁵ represents a hydrocarbon group, R⁴⁶ represents a hydrogenatom or a hydrocarbon group having 1 to 22 carbon atoms, f represents aninteger of 2 to 6, and plural —OCOR⁴⁶'s may be the same or different)

can be used.

In the general formula (XIX), R⁴⁵ represents a hydrocarbon group whichmay be linear or branched. Preferably, it is an alkyl group with 2 to 10carbon atoms. R⁴⁶ is a hydrogen atom or a hydrocarbon group with 1 to 22carbon atoms, and it is preferably an alkyl group with 2 to 16 carbonatoms.

The polyol ester represented by the general formula (XIX) can beobtained by reacting a polyhydric alcohol represented by the generalformula (XX)

 R⁴⁵(OH) _(f)  (XX)

(wherein R⁴⁵ and f are as defined above)

with a carboxylic acid represented by the general formula (XXI)

R⁴⁶COOH  (XXI)

(wherein R⁴⁶ is as defined above)

or its reactive derivatives such as its ester and acid halide and thelike.

Examples of the polyhydric alcohol represented by the general formula(XX) can include ethylene glycol, propylene glycol, butylene glycol,neopentyl glycol, trimethylolethane, trimethylolpropane, glycerin,pentaerythritol, dipentaerythritol, sorbitol and the like. Meanwhile,examples of the carboxylic acid represented by (XXI) can includepropionic acid, butyric acid, pivalic acid, valeric acid, caproic acid,heptanoic acid, 3-methylhexanoic acid, 2-ethylhexanoic acid, capricacid, pelargonic acid, caproic acid, lauric acid, myristic acid,palmitic acid, 2-methylhexanoic acid, 3-methyloctanoic acid,3-methylheptanoic acid, 2-ethylheptanoic acid, 2-methylheptanoic acid,2-methyloctanoic acid and the like.

The invention is illustrated more specifically below by referring toExamples.

EXAMPLE 1

A refrigerating machine oil composition was prepared by using apolyvinylethyl ether (a) polyisobutyl ether (b) random copolymer [aunit/b unit (molar ratio) =9/1, kinematic viscosity 68 mm²/s (40° C.),number average molecular weight 720, abbreviated as PVE] as base oil andincorporating 5% by weight, based on the total amount of thecomposition, of a polyoxybutylene (A) polyoxyethylene (B) glycolmonobutyl ether random copolymer [A unit/B unit (molar ratio)=9/1,kinematic viscosity 68 mm²/s (40° C.), number average molecular weight920, abbreviated as PAG1] as an additive. With respect to thecomposition, the flow rate decrease ratio of the capillary, the volumeresistivity and the two-layer separation temperature were measured andevaluated by the following methods. The results are shown in Table 1.

[Method for Measuring a Flow Rate Decrease Ratio of a Capillary]

An actual evaluation apparatus comprising a compressor, a capillary anda double piping-type heat exchanger was charged with a refrigeratingmachine oil composition and a refrigerant (R407C), and operated for apredetermined period of time (1,000 hours). Before and after the test,the flow rate of the capillary with a nitrogen gas was measured, and theflow rate decrease ratio was obtained.

[Method for Measuring a Volume Resistivity]

Measured at 25° C. according to JIS C 2101.

Method for Measuring a Two-layer Separation Temperature (RefrigerantCompatibility)

Sample oil and a refrigerant (R410a) were encapsulated in a glassampoule at an oil content of 10%. The temperature was progressivelyraised from room temperature, and a two-liquid interface of the sampleoil and the refrigerant was visually observed. A temperature at whichthey were separated in cloudy state was defined as the two-layerseparation temperature.

EXAMPLE 2

The evaluation was conducted as in Example 1 except that 5% by weight ofa polyoxybutylene (A) polyoxyethylene (B) glycol monobutyl ether randomcopolymer [A unit/B unit (molar ratio)=8/2, kinematic viscosity 68 mm²/s(40° C.), number average molecular weight 950, abbreviated as PAG2] wasused as an additive. The results are shown in Table 1.

EXAMPLE 3

The evaluation was conducted as in Example 1 except that 10% by weightof a polyoxybutylene (A) polyoxyethylene (B) glycol monobutyl etherrandom copolymer [A unit/B unit (molar ratio)=7/3, kinematic viscosity68 mm²/s (40° C.), number average molecular weight 1,060, abbreviated asPAG3] was used as an additive. The results are shown in Table 1.

EXAMPLE 4

The evaluation was conducted as in Example 1 except that the amount ofthe additive was changed to 2% by weight based on the total amount ofthe composition. The results are shown in Table 1.

EXAMPLE 5

The evaluation was conducted as in Example 1 except that 30% by weightof an alkylbenzene 1 [hard monoalkylbenzene, number average molecularweight 250, kinematic viscosity 15 mm²/s (40° C.), abbreviated as AB1]was used as an additive. The results are shown in Table 1.

EXAMPLE 6

A refrigerating machine oil composition was prepared by using an ester(complete ester of pentaerythritol and a mixture of 2-methylheptanoicacid (50%) and 2-methyloctanoic acid (50%)) as base oil andincorporating 10% by weight, based on the total amount of thecomposition, of PAG1 as an additive. The composition was likewiseevaluated. The results are shown in Table 1.

COMPARATIVE EXAMPLE 1

The evaluation was conducted as in Example 1 except that 10% by weightof a polyoxybutylene (A) polyoxyethylene (B) glycol monobutyl etherrandom copolymer [A unit/B unit (molar ratio)=9/1, kinematic viscosity 4mm²/s (40° C.), number average molecular weight 300, abbreviated asPAG4] was used as an additive. The results are shown in Table 1.

COMPARATIVE EXAMPLE 2

The evaluation was conducted as in Example 1 except that 10% by weightof a polyoxybutylene (A) polyoxyethylene (B) glycol monobutyl etherrandom copolymer [A unit/B unit (molar ratio)=9/1, kinematic viscosity320 mm²/s (40° C.), number average molecular weight 4,000, abbreviatedas PAG5] was used as an additive. The results are shown in Table 1.

COMPARATIVE EXAMPLE 3

The evaluation was conducted as in Example 1 except that the amount ofthe additive was changed to 30% by weight based on the total amount ofthe composition. The results are shown in Table 1.

COMPARATIVE EXAMPLE 4

The evaluation was conducted as in Example 3 except that 50% by weightof an alkylbenzene 1 [hard monoalkylbenzene, number average molecularweight 250, kinematic viscosity 15 mm²/s (40° C.), abbreviated as AB1]was used as an additive. The results are shown in Table

COMPARATIVE EXAMPLE 5

The evaluation was conducted as in Example 1 except that 1% by weight oftricresyl phosphate (abbreviated as TCP) was used as an additive. Theresults are shown in Table 1.

COMPARATIVE EXAMPLE 6

The evaluation was conducted as in Example 1 except that the additivewas not used. The results are shown in Table 1.

COMPARATIVE EXAMPLE 7

The evaluation was conducted as in Example 6 except that only the esterused in Example 6 was used. The results are shown in Table 1.

TABLE 1 Additive Number Two-layer average Mixing Flow rate Volumeseparation molecular amount decrease ratio resistivity temperatureSample weight (wt. %) of capillary (%) (Ωcm) (° C.) Ex. 1 PVE + PAG1 9205 4.5 3.70E + 12 −50° C. or less Ex. 2 PVE + PAG2 950 5 4.2 1.70E + 12−47 Ex. 3 PVE + PAG3 1,060 10 4.8 8.10E + 11  −4 Comp. PVE + PAG4 300 103.8 1.30E + 10 −50° C. or less Ex. 1 Comp. PVE + PAG5 4,000 10 6.75.60E + 12 separated at Ex. 2 room tempera- ture Ex. 4 PVE + PAG1 920 25.5 9.60E + 12 −50° C. or less Comp. PVE + PAG1 920 30 3.9 5.30E + 11−38 Ex. 3 Ex. 5 PVE + AB1 250 30 2.8 7.30E + 13 −24 Comp. PVE + AB1 25050 2.6 8.20E + 13 separated at Ex. 4 room tempera- ture Ex. 6 Ester +PAG1 920 10 8.2 9.60E + 11  −2 Comp. PVE + TCP — 1 10.9 3.80E + 13 −50°C. or less Ex. 5 Comp. PVE — 0 11.5 6.20E + 13 −50° C. or less Ex. 6Comp. Ester — 0 18.3 6.70E + 12  −7 Ex. 7

Industrial Applicability

The invention can provide a refrigerating machine oil composition bywhich a capillary tube is hardly clogged when a hydrofluorocarbon type,a hydrocarbon type, an ether type, a carbon dioxide type or an ammoniatype, preferably a hydrofluorocarbon type which can be a substitute fora chlorofluorocarbon type refrigerant problematic due to theenvironmental pollution is used as a refrigerant.

What is claimed is:
 1. A refrigerating machine oil compositioncomprising a base oil containing at least one oxygen-containingsynthetic oil selected from the group consisting of a polyvinyl etherand a polyol ester and from 1 to 20% by weight, based on the totalamount of the composition, of a polyalkylene glycol alkyl ether having anumber average molecular weight of 500 to 3,000, as represented by thefollowing general formula (I) or (II) R¹—O—(EO)_(m)(PO)_(n)—R²  (I)R¹—O—(EO)_(m)(BO)_(n)—R²  (II) (wherein EO represents an oxyethylenegroup, PO represents an oxypropylene group, BO represents an oxybutylenegroup, m and n each represent a positive number that satisfies themolecular weight, and R¹ and R² each represent hydrogen or an alkylgroup with 1 to 10 carbon atoms, provided R¹ and R² may be the same butare not hydrogens at the same time).
 2. A refrigerating machine oilcomposition comprising a base oil containing a polyvinyl ether copolymercomprising a structural unit (A) represented by the following generalformula (XVII)

(wherein R⁴³ represents a hydrocarbon group with 1 to 3 carbon atomshaving or not having an ether linkage in a molecule) and/or a structuralunit (B) represented by the following general formula (XVIII)

(wherein R⁴⁴ represents a hydrocarbon group with 3 to 20 carbon atomshaving or not having an ether linkage in a molecule) provided R⁴³ of therecurring unit (A) and R⁴⁴ of the recurring unit (B) are not the sameand from 1 to 20% by weight, based on the total amount of thecomposition, of a polyalkylene glycol alkyl ether having a numberaverage molecular weight of 500 to 3,000, as represented by thefollowing general formula (I) or (II) R¹—O—(EO)_(m)(PO)_(n)—R²  (I)R¹—O—(EO)_(m)(BO)_(n)—R²  (II) (wherein EO represents an oxyethylenegroup, PO represents an oxypropylene group, BO represents an oxybutylenegroup, m and n each represent a positive number that satisfies themolecular weight, and R¹ and R² each represent hydrogen or an alkylgroup with 1 to 10 carbon atoms, provided R¹ and R² may be the same butare not hydrogens at the same time).
 3. A refrigerating machine oilcomposition comprising a base oil containing a polyol ester and from 1to 40% by weight, based on the total amount of the composition, of analkylbenzene having a number average molecular weight of 100 to 1,000.4. A refrigerating machine oil composition comprising a base oilcontaining a polyvinyl ether copolymer comprising a structural unit (A)represented by the following general formula (XVII)

(wherein R⁴³ represents a hydrocarbon group with 1 to 3 carbon atomshaving or not having an ether linkage in a molecule) and/or a structuralunit (B) represented by the following general formula (XVIII)

(wherein R⁴⁴ represents a hydrocarbon group with 3 to 20 carbon atomshaving or not having an ether linkage in a molecule) provided R⁴³ of therecurring unit (A) and R⁴⁴ of the recurring unit (B) are not the sameand from 1 to 40% by weight, based on the total amount of thecomposition, of an alkylbenzene having a number average molecular weightof 100 to 1,000.
 5. A refrigerating machine oil composition according toclaim 4, wherein R⁴³ is an ethyl group and R⁴⁴ is an isobutyl group, andthe molar ratio of the structural unit (A) to the structural unit (B) isin the range of 95:5 to 70:30.